Deposition of fibrin in and around tumors was shown to promote invasive growth. This study extracted partially purified a procoagulant from malignant tissue but not from normal tissue. Cancer procoagulant A (CPA) is probably a serine protease that initiates coagulation by directly activating factor X. The proposed studies are to purify and study the physical, chemical and enzymatic properties of CPA. An antibody to CPA will be developed and used to study the distribution of CPA in normal and malignant tissues and in the serum of patients suspected of having cancer. Pilot studies suggest that CPA may stimulate the growth of normal cultured fibroblasts. These studies will be extended to determine dose response and response of different cell types to CPA.